Voltage regulators can be used in applications, including LED driver circuits, to generate and supply relatively constant predetermined output voltages in response to varying input voltages. FIG. 1 depicts a buck-boost switching regulator 20 configured to generate and deliver an output voltage VOutx from an input voltage VIn. In response to gate control signals VGatex, VGatey delivered to switching transistors Mx, My, energy is selectively stored and released in and between an inductor Lx and a capacitor Cx utilizing conduction pathways variously formed by the switching transistors Mx, My and a pair of diodes Dx, Dy. The buck-boost regulator 20 can be configured to generate output voltage magnitudes that are either smaller or larger than input voltage magnitudes. However, one disadvantage of this type of buck-boost converter is that the control circuitry (not shown) necessary to generate suitable gate control signals VGatex, VGatey can be undesirably complex and potentially expensive to design and fabricate.
FIG. 2 depicts a linear regulator configuration 24 commonly referred to as a low-dropout (LDO) regulator 24. A negative feedback loop formed by an amplifier Ax and an output transistor Mz can generate and deliver an output voltage Vouty, having a predetermined value as a function of a reference voltage Vrefx, into a capacitor Cy from the input voltage VIn. The LDO regulator 24 can generally only deliver output voltage magnitudes less than received input voltage magnitudes. The depicted LDO regulator also has additional disadvantages, beyond being unable to boost voltages, including being relatively power inefficient, due to power being dissipated in proportion to the voltage drop between the input and output voltages Vin, Vouty and an associated current through the output transistor Mz. This power inefficiency becomes an increasing concern with increasing voltage magnitude differences between the input and output voltages VIn, Vouty.
Thus, there exists a need for voltage converters, including to drive LEDs, that are capable of selective voltage boosting, having reduced complexity and cost, and being power efficient.